Abstract Over the past ten-fifteen years there has been a continuous increase in the interest in quality of life research. There is a huge increase in the number of clinical trials applying quality of life as an outcome measure and also in the number of studies where assessment of quality of life is the main focus of the research. During the last decades the resources of health care has increasingly been directed towards the care of chronically ill patients. In these conditions several symptoms persist or may even worsen even with effective therapy. This provides an explanation why quality of life has become an important and useful outcome measure complementing the traditional "hard outcomes" such as morbidity and mortality. Assessment of quality of life is also an important component of cost-effectiveness studies and health-technology assessment. Recently, the overall quality of quality of life research has improved significantly. In the early days, several instruments were used without any rigorous methodological assessment of the instrument itself. At present there are a number of meticulously developed and well documented instruments available with their reliability and validity evaluated with psychometric methods in different patient's populations. When one wants to use one of these measures in a different cultural environment or in a different language one faces several difficulties and a rigorous methodology needs to be followed when translating and validating quality of life tools. In this review the authors discuss the significance of quality of life assessments and list some practical issues concerning the methodology of quality of life studies. Finally they provide a short description of the most commonly used instruments and will give a reference of the scales available in Hungarian.